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Old 17th March 2007, 07:30 PM   #5991
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I don't want to abuse your patience (I can see Brent smiling) but would you treat me as a bewildered, rather slow-witted newbie who has to be led by the hand (it's good for your egos):
Brent used the bb2134 originally and I liked them but got that awful itch so bought a pair of 627's. As I already posted, I probably did them a mischief by first plugging them in wrong way round (maybe this accounts why I don't like the sound?). Don't ask me how and don't tell me to put the others back cause I crapped them getting them loose. I didn't hear about the caps
(hey this thread is hours and hours of reading!) So if you were really the gentleman that I know you to be
you will send or paste a nice couple of hi rez pics for me to ponder (you can hold the soldering iron too if you want)! Would these caps apply equally to the 4562's??? Og God why don't I ever leave well enough alone??? That would make for a good DIY epitaph.
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Old 17th March 2007, 08:12 PM   #5992
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Good evening guys,

I also find strange the turn back about the LM4562... I don't have time and any wish to listen to opamps for hours, and the simple aim of my mods is really reached with these, better than my former AD8620. If I derserve a better sound I would have bought an overall better system. I think too many people like them and now It's better to say you don't but Glenn who always had strange taste
As one of the most stupid about electronics and with the less good amp/speakers I find the LM4562 fantastic, and very handy direct fit. I do hope a tube high class CDP is far better...

Anyway, My question was about the Flea's PSU (Martin are you around?): mine delivers 17.88V, when the Flea's manual says "minimu 18V" and a "minimum minimum 17.6V"... I'm between the minimum and the minimum minimum... (you see why LM4562 fits me?)

Thanks...
Shepp, still want a pair of LM4562? The caps are between pin 4 and 8, under the PCB is nice, I have MKS2 0.1F there but I was advised (Simon) my 1F will do better.
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Old 17th March 2007, 08:16 PM   #5993
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bien sur! Je ne comprends rien de ce qu'ils disent mais je veut tout essayer
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Old 17th March 2007, 09:08 PM   #5994
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Quote:
Anyway, My question was about the Flea's PSU (Martin are you around?): mine delivers 17.88V, when the Flea's manual says "minimu 18V" and a "minimum minimum 17.6V"... I'm between the minimum and the minimum minimum...
Right here

Don't worry that shuld work OK.

The 17.6v figure is the lowest that is guaranteed to work with tolerances of parts - but not the raw PSU - taken into account:

7812 puts out 12.0v nominal, raised from ground by the LED - 1.95v actual, say 2V = 14.0v;
7812 dropout needs to be 2.2-2.5v min at low currents;
Gyrator portion drops 0.65v+ small amount through bias network to drive BC547. How much? well it's the output current - say 20mA - divided by Hfe, say 300 (pessimistic for a BC547C at 20mA). That's 67uA, or 0.67V across the 10K biasing resistor.

So we need (14.0+2.5+1.3v) input, 17.8V, to guarantee it will work. In fact, because the BC54x will have a Hfe of c.400 at these currents, most LM7812s are actually about 11.9v to avoid exceeding their rated voltage (and fwill work with 2.3v overhead at 10mA output) and the LED voltage reduces at -2mV/degreeC, 17.6 will work - always, but that's why it's given as 'minimum minimum'; it gives no allowance for variation in the output of the raw PSU.

If you're worried that your implentation is a bit marginal, then monitor the output from the 7812. It should be constant to two decimal places at (around 13.9v, +/- a little bit). If you see it wandering by 10mV or more over a few minutes then it has insufficient voltage input, and the fix is either more raw input, or reduce R1 (say to 5K ) and try again.
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Old 18th March 2007, 04:53 AM   #5995
awpagan is offline awpagan  Australia
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It's all you fault Ray,
well almost, plus a few others

there was a good question from Glenn2
has anyone tried the zapfilter2????

It does look interesting, discrete and no output cap also balanced
problem is smd's

the schematic's available, might see about doing a version for myself.

allan

ps i do understand the layout will not be as good as the original but
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Old 18th March 2007, 06:45 AM   #5996
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Default Zap Filter

For those unfamiliar with the Zap Filter...


http://www.lcaudio.com/index.php?page=6




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Old 18th March 2007, 06:48 AM   #5997
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Default Zap Filter

The Zapfilter adds quite a bit of complexity to the system when compared to a discrete output stage.

It's main advantage is the provision of a balanced output but how many of us actually use balanced amps ?

Andy
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Old 18th March 2007, 06:51 AM   #5998
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Default Balanced output from Discrete stage

It would not be that hard to add another follower to the discrete output stage in order to give a balanced output.

Andy
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Old 18th March 2007, 06:52 AM   #5999
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nearly at 6000
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Old 18th March 2007, 06:53 AM   #6000
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so who got it ?

ME!!


==========================================

Hello to all contributors to this great thread.

It has been a credit to all for the lack of backbiting etc. and the very good natured responses even when some of the questions have been from inexperienced DIYers.

See you at the UK DIYAudio Fest?

Andy
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